CERN-LHC. The W boson helicity fractions from top quark decays in top quark pair events are measured using data from proton-proton collisions at a centre-of-mass energy of 8 TeV. The data were collected in 2012 with the CMS detector at the LHC, corresponding to an integrated luminosity of 19.8 fb-1. Events are reconstructed with either one muon or one electron, along with four jets in the final state, with two of the jets being identified as originating from b quarks. The measured helicity fractions from both channels are combined, yielding F0=0.681 +/- 0.012 (stat) +/- 0.023 (syst), FL=0.323 +/- 0.008 (stat) +/- 0.014 (syst), and FR= -0.004 +/- 0.005 (stat) +/- 0.014 (syst) for the longitudinal, left-, and right-handed components of the helicity, respectively.
|Date made available||2016|